MAX1775 19-1811 Rev 2 4/09 Dual-Output Step-Down DC-DC Converter for PDA/Palmtop Computers General Description Features The MAX1775 dual, step-down DC-DC converter gen- Dual, High-Efficiency, Synchronous Rectified erates both the main (+3.3V at over 2A) and core Step-Down Converter (+1.8V at up to 1.5A) supplies for a complete power Main Power solution for PDAs, subnotebooks, and other hand-held Adjustable from +1.25V to +5.5V devices. The main output is adjustable from +1.25V to Over 2A Load Current +5.5V. The core output is adjustable from 1V to 5V. Up to 95% Efficiency Both switching converters operate at up to 1.25MHz for small external components and use synchronous recti- Core Power fiers to achieve efficiencies up to 95%. Operation with Adjustable from 1V to 5V up to 100% duty cycle provides the lowest possible Internal Switches dropout voltage to extend useful battery life. Up to 1.5A Load Current The MAX1775 accepts inputs from +2.7V up to +28V, Up to 92% Efficiency allowing use with many popular battery configurations as 100% (max) Duty Cycle well as AC-DC wall adapters. Digital soft-start reduces Up to 1.25MHz Switching Frequency battery current surges at power-up. Both the main and Input Voltage Range from +2.7V to +28V core converters have separate shutdown inputs. The MAX1775 comes in a small 16-pin QSOP package. 170A Quiescent Current The MAX1775 evaluation kit is available to help reduce 55A Shutdown Current design time. Digital Soft-Start Independent Shutdown Inputs Ordering Information Applications PART TEMP RANGE PIN-PACKAGE Hand-Held Computers MAX1775EEE -40C to +85C 16 QSOP PDAs Internet Access Tablets Typical Operating Circuit POS Terminals Subnotebooks IN 2.7V TO 5.5V (28V IN CASCADE) IN CVH INC ON Pin Configuration OFF SHDNM PDRV ON OFF SHDNC MAIN TOP VIEW 3.3V OVER 2A NDRV SHDNM 1 16 LXC CVL SHDNC 2 15 INC MAX1775 CS+ PGND 3 14 GND CS- REF FBM MAX1775 NDRV 4 13 FBC CORE CVL 5 12 CS- LXC 1.8V PGND 1.5A GND IN 6 11 CS+ PDRV 7 10 FBM FBC CVH 8 9 REF 16 QSOP Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim s website at www.maxim-ic.com. EVALUATION KIT AVAILABLEDual-Output Step-Down DC-DC Converter for PDA/Palmtop Computers ABSOLUTE MAXIMUM RATINGS IN, SHDNM, CVH to GND.......................................-0.3V to +30V Continuous Power Dissipation 16-Pin QSOP (derate 7.1mW/C above +70C)..........571mW IN to CVH, PDRV ......................................................-0.3V to +6V PDRV to GND..................................(V - 0.3V) to (V + 0.3V) Operating Temperature .......................................-40C to +85C CVH IN Storage Temperature.........................................-65C to +150C PGND to GND .......................................................-0.3V to +0.3V Lead Temperature (soldering, 10s) .................................+300C All Other Pins to GND...............................................-0.3V to +6V Core Output Short Circuit...........................................Continuous Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +12V, V = V = V = V = +3.3V, V = +1.8V, Circuit of Figure 4, T = 0C to +85C, unless otherwise noted. IN MAIN INC CS- CS+ CORE A Typical values are at T = +25C.) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Voltage V 2.7 28 V IN V = +1.5V, V = +1.5V, FBM FBC Input Quiescent Supply Current I 15 30 A IN V = V = +3.3V SHDNM SHDNC V = +1.5V, V = +1.5V, FBM FBC CS- Quiescent Supply Current I - 110 220 A CS V = V = +3.3V SHDNM SHDNC Core Regulator Quiescent V = +1.5V, V = +1.5V, FBM FBC I 60 120 A INC Supply Current V = V = +3.3V SHDNM SHDNC IN Shutdown Supply Current SHDNM = SHDNC = GND 5 30 A MAIN REGULATOR Main Output Voltage Adjust 1.25 5.5 V Range FBM Regulation Threshold V V = 0 to +60m V , V = + 2.7V to +2 8V 1.21 1.25 1.29 V FBM (C S + - C S - ) IN FBM Input Current I V = +1.3V -0.1 0.1 A FBM FBM Current-Limit Threshold V V - V 60 80 100 mV CLM CS+ CS- Minimum Current-Limit V V - V 615 24 mV MIN CS+ CS- Threshold Valley Current Threshold V V - V 40 50 60 mV VALLEY CS+ CS- Zero Current Threshold V V - V 015mV ZERO CS+ CS- PDRV, NDRV Gate Drive V = +3.3V, I = 50mA 2 4.4 CS- LOAD Resistance CS- to CVL Switch Resistance I = 50mA 4.5 8 CVL PDRV, NDRV Dead Time 50 ns Maximum Duty Cycle 100 % Minimum On-Time 200 400 650 ns Minimum Off-Time 200 400 650 ns 2 MAX1775